Vivienne Nathanson: 'Some primary care trusts are apparently making it so hard for patients to opt out'. Photograph: Chris Young/PA

Patients who do not want their medical records to be placed on a national electronic database are being coerced by NHS managers to give their consent, the British Medical Association said last night.

During trials of the scheme in Birmingham and Stoke-on-Trent, thousands of patients are being told they cannot opt out unless they make an appointment with "NHS advisers" to explain face to face why they do not want to take part.

Dr Vivienne Nathanson, the BMA's head of science and ethics, said: "It's surprising and very worrying that some primary care trusts are apparently making it so hard for patients to opt out.

"The onus is on them to explain the benefits of the care records scheme to patients. They should not applying any kind of pressure. If it requires that kind of coercion, it's not real consent."

Health ministers promised that patients would be able to opt out after the Guardian raised concerns in 2006 about a plan to store the records of 50 million patients in England on a national database known as the Spine.

Evidence of obstacles being put in the way of patients wanting to opt out came in reply to an application under the Freedom of Information Act by the GPs' newspaper, Pulse.

It obtained letters to patients written by the chief executives of NHS South Birmingham and NHS Stoke-on-Trent saying patients should get information on "drop-in sessions" with "NHS advisers".

An NHS South Birmingham spokesman said: "Patients are asked to opt out, in person with their GP, for the GP to ensure the patient understands all the implications and to answer any questions."

An NHS Stoke-on-Trent spokeswoman said: "We considered it more secure to ask patients to come in to the surgery to complete the form, as this would give reception staff the opportunity to confirm their identity, either formally or informally."